A milling machine is a machine tool used to machine solid materials. Unlike a drill press that holds a work piece stationary as the drill moves axially to penetrate the material, milling machines also move the work piece radially against the rotating milling cutter (milling tool), which cuts on its sides as well as its tip. Work piece and cutter movement are precisely controlled to less than 0.001 in (0.025 mm), usually by means of precision ground slides and screws, and the like. Milling machines may be manually operated, mechanically automated, and/or digitally automated via computer numerical control.
Milling machines can perform a vast number of operations, from simple (e.g., slot and keyway cutting, planing, drilling) to complex (e.g., contouring, die sinking)
Milling machines include multiple holders that are used to hold the milling cutters or tools. These tools can be changed out when different tools are needed, such as when replacements for defective tools and/or when different types of tools are needed from what originally existed in the holders.
Changing out milling tools is a time consuming process because conventionally, the holders are first removed from the milling machine and then placed in other devices to steady the holders while the tools are swapped out of the holders for other tools. Then, the holders with the other tools are placed back in the milling machine.
This entails no less than four steps: 1) removing the tool holder; 2) removing the existing tool from the tool holder; 3) inserting a replacement tool into the tool holder; and 4) re-inserting the tool holder into the milling machine.
One positive aspect of the process is that the milling machine tool holders are for the most part standardized to a particular standard, referred to as cat 40.